Vitamins are a kind of trace organic substance that must be obtained from foods to maintain normal physiological functions of living organisms. They play an important role in the growth, metabolism and development of human body. Synthesis of vitamins in vitamin production has an increased proportion year by year, and a selective hydrogenation of alkynol substances is one of the most important reactions in vitamin production. Supported Pd catalysts are commonly used in these reactions. At present, a catalyst for the hydrogenation reaction of the alkynol substances in industrial production is mainly a Lindlar catalyst. However, the Lindlar catalyst still has many disadvantages such as high toxicity, poor stability of water phase and insufficient selectivity. It is urgent to develop a more efficient and stable catalyst for selective hydrogenation of the alkynol substances.
Recently, Pd-based alloy catalysts have attracted extensive attention in the field of hydrogenation of the alkynol substances, especially Pd-based alloy catalysts obtained by high-temperature hydrogen reduction with a reducible oxide as a support. However, such catalysts generally have problems such as low specific surface area, and a formation of these alloys will reduce Pd sites exposed on its surface, thereby reducing catalytic activity. The carbon material has a large specific surface area, is easy to control and an ideal catalyst carrier. Compared with an ordinary carbon material, nitrogen-doped carbon material has some unique advantages. For embodiment, a doping of nitrogen can change a local electronic structure of carbon materials, which is beneficial to a dispersion of noble metal nanoparticles; it will enhance an activity and stability of the catalyst through a mutual interaction between nitrogen and metals. However, how to combine the advantages of the two carriers and prepare a metal oxide and nitrogen-doped porous carbon alloy composite catalyst loaded Pd in high dispersion with unique performance still has enormous challenges. Recently, Wang et al. (J. Catal. 2017, 350, 13-20) developed a PdZn/CN coated ZnO catalyst based on a theory that Pd particles on edge and corner positions can cause an excess-hydrogenation of the alkynol. Zn poisons the edge and corner positions of Pd particles, but this poisoning is not selective, and Zn atom also occupies a flat position, causing a decrease of catalyst activity.